hw_breakpoint: Simplify *register_wide_hw_breakpoint()

1. register_wide_hw_breakpoint() can use unregister_ if failure,
   no need to duplicate the code.

2. "struct perf_event **pevent" adds the unnecesary lever of
   indirection and complication, use per_cpu(*cpu_events, cpu).

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155018.GA6347@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 9c71445328aff6cdc6fd5f8dcc5406bfd8ba36f7..38418f786f36f40d4efd0532282c36912853cd7d 100644 (file)
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -497,8 +497,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
                            perf_overflow_handler_t triggered,
                            void *context)
 {
-       struct perf_event * __percpu *cpu_events, **pevent, *bp;
-       long err;
+       struct perf_event * __percpu *cpu_events, *bp;
+       long err = 0;
        int cpu;
 
        cpu_events = alloc_percpu(typeof(*cpu_events));
@@ -507,31 +507,21 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
 
        get_online_cpus();
        for_each_online_cpu(cpu) {
-               pevent = per_cpu_ptr(cpu_events, cpu);
                bp = perf_event_create_kernel_counter(attr, cpu, NULL,
                                                      triggered, context);
-
-               *pevent = bp;
-
                if (IS_ERR(bp)) {
                        err = PTR_ERR(bp);
-                       goto fail;
+                       break;
                }
-       }
-       put_online_cpus();
-
-       return cpu_events;
 
-fail:
-       for_each_online_cpu(cpu) {
-               pevent = per_cpu_ptr(cpu_events, cpu);
-               if (IS_ERR(*pevent))
-                       break;
-               unregister_hw_breakpoint(*pevent);
+               per_cpu(*cpu_events, cpu) = bp;
        }
        put_online_cpus();
 
-       free_percpu(cpu_events);
+       if (likely(!err))
+               return cpu_events;
+
+       unregister_wide_hw_breakpoint(cpu_events);
        return (void __percpu __force *)ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
@@ -543,12 +533,10 @@ EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
 void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
 {
        int cpu;
-       struct perf_event **pevent;
 
-       for_each_possible_cpu(cpu) {
-               pevent = per_cpu_ptr(cpu_events, cpu);
-               unregister_hw_breakpoint(*pevent);
-       }
+       for_each_possible_cpu(cpu)
+               unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
+
        free_percpu(cpu_events);
 }
 EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);